Double-diffused drain (DD) and lightly-doped drain (LDD) structures have been proposed during the past few years to improve the high-field effect characteristics of submicron MOSFETs. Compairsions of DD and LDD devices have been made by several investigators who have analyzed advantages and disadvantages of each. A variety of structural configurations for LDDFETs have been proposed and fabricated.
It is an object of the present invention to provide a novel field effect transistor in which highly-doped depending source and drain regions are provided with lightly-doped sheaths.
It is also an object to provide such a transistor which may be readily fabricated and which provides latchup suppression and improved high field effects.